9th May 2019
HMRC are currently experiencing issues with the Developer sandbox environment. A number of microservices are not available resulting in a partial outage. For example, your Sandbox applications may not be visible in the Developer Hub. HMRC are looking to identify a fix.
You can check for issues by clicking on the ‘Service availability’ link at the top of the Developer Hub, where you can also subscribe for updates on the availability of the API platform.